Method for the flotation of finely divided minerals



NERALS D. WESTON Aug. 24, 1965 METHOD FOR THE FLOTATION OF FINELY DIVIDED MI 6 Sheets-Sheet 1 Original Filed Jan. 21, 1959 A va/r02 14 515 704/ D. WESTON Aug. 24, 1965 METHOD FOR THE FLOTATION OF FINELY DIVIDED MINERALS 6 Sheets-Sheet 2 Original Filed Jan. 21, 1959 12 LIQUID LIQUID 7 All? /A v/vro2 Dav/0 WESTON flrraelvsxs 1965 D. WESTON 3,202,281

METHOD FOR THE FLOTATION OF FINELY DIVIDED MINERALS Driginal Filed Jan. 21, 1959 6 Sheets-Sheet 3 AIR l AIR L/Ol/ID 45 LIQUID Annex ro e 0/! W0 Wes 70/V ELM/KW D. WESTON Aug. 24, 1965 METHOD FOR THE FLOTATION OF FINELY DIVIDED MINERALS 6 Sheets-Sheet 4 Original Filed Jan. 21, 1959 /A v5 70 1Q. .04 V/D ro/v Z/W 72/ D. WESTON Aug. 24, 1965 METHOD FOR THE FLOTATION OF FINELY DIVIDED MINERALS 6 Sheets-Sheet 5 Original Filed Jan. 21, 1959 R M m .3 w i. W l q ne m 1 m HELICAL CLASSIFIER BALL MILL Aug, 24, 1965 D. WESTON Original Filed Jan. 21, 1959 6 Sheets-Sheet 6 ii II QI5Z -101 100 L MAKE-UP WATER 110 I TAIL //v 1/51/7012 04 W0 Wzsro/v United States Patent M 3,2tl2,281 METHOD FOR THE FLOTATION 0F FlNELY DIVHDED MENERAL'S David Weston, 129 Adelaide St. W., Toronto,

@ntario, Canada Continuation of application Ser. No. 788,175, Jan. 21,

1959. This application Get. 1, 1964, Ser. No. 400,817

Claims. (Cl. 2tl9-166) This application is a continuation of my copending application Serial No. 788,175, now abandoned, filed January 21, 1959.

This invention relates generally to the application of reagents to finely divided particulate materials while the latter are suspended in a liquid pulp. More particularly, in its primary application the invention relates to the application of reagent to such materials in order to prepare the latter for a subsequent flotation step in which one or more constituents of the material are to be concentrated.

Certain materials are generally regarded as refractory to flotation. These include such materials as manganese oxides, iron oxides, oxidized sulphides of lead, copper and zinc, and many others. Various attempts have been made to concentrate such materials by flotation and in general, although concentration can be achieved in most cases, reagent consumption is high and recoveries and grades of concentrate are comparatively low, so that economically acceptable operation of such processes has in general not been satisfactory. One feature of many such materials is that in many cases in addition to naturally occurring slimes, reduction of the material to an appropriate stage of mineral liberation involves the production of a considerable additional quantity of slimes, which it has heretofore been necessary to eliminate prior to flotation, resulting in a substantial amount of the head value of the material being lost with the slimes which are eliminated.

It has recently been shown that in at least some instances it is possible to float slimes through the use of exorbitantly high concentrations of reagent or through 32%,281 Patented Aug. 24, 1965 Broadly speaking according to the invention, the foregoing concept is put into practice by suspending the particulate material to be treated in a first liquid to form a pulp, and establishing and maintaining Within the said pulp a localized zone of concentrated reagent activity into which the reagent is fed as a finely divided mechanical dispersion in the form of a second liquid which is immiscible with said first liquid at least to the extent necessary to maintain the droplets of reagent as a separate phase for the conditioning period, while the pulp is progressively passed through said zone.

The level of available energy possessed by the particles of reagent may be influenced in many different ways. To begin with, the formation of a finely divided mechanical dispersion creates available energy at the surface of the reagent particles which is of a higher order of potential the smaller the particle. This energy is in very many cases sufficient to overcome the existing forces of the solid liquid interface of the particles of material. Where a higher level of available energy is required, this may be supplied within the zone of concentrated reagent activity by elevation of temperature, pressure, or both, by raising the kinetic energy of the. pulp within said zone by agitation or the creation of conditions of elevated or extreme turbulence, by the application of sonic, supersonic or ultrasonic vibration, or where applicable, the application of static or alternating electrostatic or electromagnetic fields. Alternatively to the foregoing or in conjunction therewith, the available energy of the reagent particles may be increased by introducing the reagent as a water soluble substance dissolved in a water insoluble vehicle. In this case, as the reagent droplets become mixed with the liquid of the pulp the Water soluble reagent within the dropletswill seek to distribute itself on either side of the interface boundary, and there will thus be established surrounding each droplet a zone of high reagent concentrathe use of certain special reagents with a very long period of conditioning. Neither system can be regarded as economically satisfactory as long conditioning times are costly both in power consumption and in capital cost and maintenance cost of the plant involved. Where flotation of slimes is achieved by the use of exorbitantly high reagent concentrations, the ,cost of the reagent consumed is frequently higher than the Worth of the values recovered from the slimes.

The present invention provides a means of activating refractory materials, and in particular materials associated with slimes in a much shorter period of time than has heretofore been possible, and with greatly reduced reagent consumption. The invention, while leading to outstanding benefits in relation to refractory ores and slimes, is generally applicable to all types of material and is capable of producing reduction of reagent consumption and/or increases of recovery and/or grade in almost all cases.

Broadly speaking, the invention is based upon the novel conception that reagent may successfully and rapidly be applied to refractory particles, including slimes, by firstly having the reagent in finely subdivided form in a physical condition in which at least during its period of application it is capable of existing as a liquid phase separate from the liquid of the pulp, and secondly by the maintenance in such particles of reagent at least during. the period of application thereof of a level of energy in relation to the particulate material being treated sufficient to override the existing inter-action of forces at the solid liquid interface between the particles of material and the pulp liquid. t

of reagent within such :zone being sufiicient to overcome the forces acting at the solid liquid interface of particles to be treated.

In order for the droplets of the reagent dispersion to be maintained as a separate liquid phase during passage through the zone of concentrated reagent activity it is not necessary that the reagent droplets be entirely immiscible With the pulp liquid, it is only necessary that there be sutlicient immiscibility that a phase boundary between the two liquids is preserved for a final period which corresponds at least to the time it takes the reagent particle to pass through the zone. This may in some cases be extremely short i.e.- of the order of a few milliseconds. In the absence of a conventional term to express the required degree of immiscibility, the required degree is referred to herein as being effective immiscibility, the reagent being described as effectively immiscible with the pulp liquid. t

It Will be appreciated that as in all operations which relate to the treatment of naturally occurring materials the treatment of any particular material will involve an appropriate selection of the reagents and the conditions of application thereof in order to secure the best and most economical result.

Various ways are available in which to form a mechanical dispersion of the reagent. One suitable method is to form such dispersion in a stream of air or other gas inert to the proposed conditioning operation by means of a fog nozzle. The resulting air dispersion may then be introduced to the zone of concentrated reagent activity in the pulp either in the body of the pulp, or to the air intake of a flotation machine or in various other ways of a number of which will be hereinafter described. Instead of forming the dispersion in a stream of air or inert gas, it may be found desirable to introduce the dispersion in a stream of soluble gas such as carbon dioxide. Alternatively, the reagent may be introduced by means of a steam line either by forming a mechanical suspension of droplets in the steam itself Where the reagent is substantially insoluble in steam or does not vaporize therein, or in the case where the reagent is soluble or unstable in steam or vaporizes at the temperatures of the steam line, simply by feeding the reagent in metered quantities to the steam so that as the steam condenses within the zone of concentrated reagent activity the reagent is left as a mechanical dispersion in the pulp as it condenses. It will be appreciated that introduction of the reagent in a steam line will produce a very high degree of kinetic energy in the zone of concentrated reagent activity owing to the shock waves produced by the condensing steam.

Instead of using air or gas or vapor as a vehicle for the dispersion of reagent, such dispersion may be formed utilizing a liquid vehicle, the latter being either a liquid readily miscible with the liquid of the pulp, water, or pulp liquid which is recycled, e.g. from a filtration or other dewatering stage of the process involved. Such dispersion can be formed by means of high speed mechanical impellers placed in the feed line or by forcing concurrent streams of the reagent and vehicle through appropriately designed mixing chambers of conventional construction. it is important particularly where liquid vehicles are used that the formation of the dispersion take place as closely as possible to the point of introduction of the dispersion to the zone of concentrated reagent activity in the pulp, so that the surface energy created on the dispersed droplets has as little time as possible to dissipate before introduction thereto. he use of emulsifying agents and other surface active agents to promote dispersion is to be avoided as the latter tend to maintain intact the face boundary between the dispersed reagent and the vehicle with the consequence that the surface energy produced by the creation of the dispersion is in effect neutralized and is not available to assist in the displacement of the solid liquid interface at the surface of the particles of material. In order to distinguish the type of dispersions preferred in the practice of the present invention from stabilized dispersions such as colloids and emulsions which have been stabilized with surface active agents, I refer herein to such dispersions as are preferred in the practice of the invention as dynamic dispersions.

A preferred manner of employing the present invention embodies the formation of the zone of concentration of reagent activity within one or more mixing chambers placed in a line through which the pulp is fed by appropriate means. A preferred application of energy to the said zone in this instance is through the use of a concentration of ultrasonic energy provided by ringing a number of supersonic generators around the outside of the mixing chamber as will hereinafter be described. In this instance the feed lines for the dispersion of reagent will enter the mixing chamber at the throat thereof, and the application of ultrasonic energy may be made just prior to or just after the introduction of the reagent dispersion or both. A particular advantage of this embodiment of the invention resides in the fact that the use of ultrasonic frequencies Within the relatively small enclosed space of the mixing chamber tends to disassociate particles of slime from larger particles of particulate material to which they may be adhering, and thus said particles become freed for independent application to them of the reagent.

The invention now having been described in some of its broader aspects, a better understanding of its applica tion may be had by reference to the following detailed explanation of its application by means both of conventional apparatus and of novel apparatus particularly adapted to carry it out. a The application of the invention will be described in conjunction with the accompanying drawings wherein:

FIG. 1 is a vertical cross section of a conditioning tank wherein a zone of concentrated reagent activity is provided near the bottom of the tank in the region of the impeller;

FIG. 2 is a horizontal section taken at Z--2 of FIG. 1;

FIG. 3 is a vertical cross section of a conditioning tank illustrating application of a reagent dispersion to the vortex thereof;

FIG. 3a is a vertical cross section of a floatation tank wherein a zone of concentrated reagent activity is obtained in the vortex and in the region of the impeller by introduction of an air dispersion of reagent into the airstream thereof;

FIG. 4 is a vertical cross section of a floatation tank into which an air despersion of reagent is introduced downwardly at points below the surface of the liquid through downwardly directed nozzles to create a zone of concentrated reagent activity immediately below such nozzles;

FIG. 5 is a partly diagrammatic fragmentary perspective of a system for introducing a dispersion of reagent to a pipe containing the particulate material in the form of a pulp;

FIG. 6 illustrates diagrammatically the introduction of a suspension of reagent in the throat of a venturi;

FIG. 7 illustrates the introduction of a dispersion of reagent to a line carrying a pulp containing the particulate material to be treated;

FIG. 8 is a diagrammatic View of suitable apparatus for the formation of the zone of concentrated reagent activity within a mixing chamber placed in a line through which the pulp is flowing;

FIG. 9 is a diagrammatic illustration of a specially designed mixing chamber which is adapted to provide the application of supersonic or other energy to the material both before and after introduction of the reagent;

FIG. 10 illustrates a leaching circuit utilizing the process of the invention;

FIG. 11 is a diagrammatic perspective of the application of reagent to a ball mill to provide a zone of concentrated reagent activity along a line coinciding with the toe of the charge;

FIG. 12 is a section taken along the plane AA of FIG. 11;

FIG. 13 is a diagrammatic illustration in plan of the application of a number of zones of concentrated reagent activity at selected points in a milling system consisting of a primary ball mill and a classifier.

Referring now more particularly to the drawings in FIG. 1, there is depicted the establishment of a zone of concentrated reagent activity in the area of the impeller of a conventional type of conditioning tank. The tank 10, which is of a generally conventional construction, is

equipped with a propeller type impeller 11 mounted on the shaft 12 and driven at a comparatively high rate of speed by electric motor 13 through the V-belt drive 14. Extending upwardly from the bottom 15 of the tank are four dispersion nozzles 16 which project upwardly and inwardly in the bottom of the tank being directed at a central point at the region of the bottom of the impeller 11. Each of the nozzles 16 is supplied with liquid reagent and air through the lines 17 and 18 respectively.

The arrangement illustrated in FIG. 1 is suitable for the application of a xanthate to ores which contain, e.g. copper sulphides combined with copper oxide, or the sulphidization of lead carbonate by means of hydrogen sulphide gas.

In using this arrangement to apply a xanthate, a suitable xanthate is dissolved in fatty acid by dissolving the pure or substantially pure xanthate in such fatty acid to form as concentrated a solution as is possible without impairing the liquidity of the fatty acid beyond the point where the solution can be fed as a liquid in the liquid line 17 of the nozzles 16; Air is fed through the air lines 18, and the rates of liquid feed and air feed are adjusted to produce a fine air dispersion of droplets of the reagent which is injected into the zone 19 just below the impeller. The droplets of reagent maintain a phase boundary with the liquid in the pulp in the conditioning tank It) and the xanthate, being water soluble, tends to distribute itself on either side of this phase boundary, thereby forming around each droplet a zone of concentrated aqueous solution of xanthate. Thus, there is formed within the zone 19 a myriad of dispersed minute zones of concentrated xanthate solution, which meet the downcoming pulp in such a way that each particle of mineral, even if it is in the slime range of size, will physically impinge upon at least one such zone of high xanthate concentration and become conditioned by the xanthate. When sufficient reagent has been added and the operation is of the batch type, the reagent and air supply may be cut off for a further period of conditioning, if necessary, and the air may then be turned on again and the values floated with the fatty acid acting as a flotation agent either by itself or with the addition of a conventional frother.

The advantage of the invention in an operation such as that which has just been described resides in the fact that the xanthate is brought int-o contact with the individual particles of slime at a concentration which is capable of enabling the xanthate to displace the solid liquid interface on the slime particles, so that when flotation is subsequently carried out, the slimes will float in the same manner as the larger particles. In addition, the fatty acid acts as a collector for the copper oxide enabling a practical float to be achieved with ores not hitherto considered amenable to practical concentration by flotation.

In the case where the arrangement described is to be used for the sulphidization of, for instance, lead carbonates, hydrogen sulphide is dissolved in fatty acid at elevated pressure and the hydrogen sulphide-fatty acid solution is fed .to the liquid lines 17 in the same manner as just described for the operation using xanthate solution. The nozzles 16 inject an air suspension of droplets of the hydrogen sulphide-fatty acid solution into the zone 19. As the suspension leaves the nozzles -16, the hydrogen sulphide commences coming out of solution in the droplets of fatty acid owing to the release of the pressure, thus forming concentrations of hydrogen sulphide at the interfaces of the droplets as the latter are meeting the particles of downwardly moving pulp. Thus, each particle of lead carbonate as it impinges on a droplet of fatty acid is exposed to a high concentration of H 8 suflicient to bring about sulphidization and render it amenable to concieintration subsequently by conventional flotation mesh- 0 s.

FIG. 3 illustrates another :means by which reagents of the type just disclosed may be fed to a conditioning tank. In FIG. 3, which depicts a conventional conditioning tank of the same type illustrated in FIGS. 1 and 2, the nozzles .16 discharge into the air above the vortex formed by the action of the impeller 11, establishing a zone of concentrated reagent activity which extends vertically into the vortex and down the sides of the shaft '12 into the region of the impeller. As Will be apparent, the main difference in operation as between that described in relation to FIG. 1 and that described in relation to FIG. 3 is that a good deal less air is forced into the pulp when the nozzles are directed into the vortex as illus .trated in FIG. 3 than is the case when the latter are directed directly into the pulp itself. This is an advantage where it is desired to have a minimum of frothing during the conditioning period.

In FIG. 3a, which represents a conventional flotation cell, the parts whereof are similar to the parts of the conditioning tank illustrated in FIGS. 1 to 3 (and similarly numbered) with the exception that the impeller shaft 12a is hollow and provided with air holes as is conventional with flotation impellers. In this case, the nozzle 16 is directed downwardly into the interior of the impeller from the top thereof and the zone of concentrated reagent ac tivity surrounds the impeller shaft and impeller. It will be convenient to carry out the invention in the manner illustrated in FIG, 3a wherever it is intended to combine the conditioning with flotation in the same vessel.

A still further adaptation of conventional equipment for the carrying out of the process of the invention is illustrated in FIG. 4 where a conventional agitator equipped with agitator blades 41 mounted on hollow shaft 42 driven by motor 43 through V-belt drive 44 is provided with the nozzles 45 which are directed downwardly beneath the level of pulp in the apparatus, thus establishing a zone 46 of concentrated reagent activity in a man- .ner similar to that described in relation to the foregoing embodiments. When conditioning is complete, air may be introduced through the hollow shaft 42 in order to accomplish flotation with or without the addition of conventional frothers and other flotation agents.

In the embodiment illustrated in FIG. 5, an air suspension of reagents is injected into the pipe line 50 which is carrying a pulp of the material to be treated under the influence of the sludge pump 51. The reagent dispersion is introduced into the flowing pulp by means of the nozzles 52 each of which is fed by an air line 53 and the liquid line 54. As the amount of air injected is very small in relation to the total pulp insufiicient air is injected to cause formation of air locks in the sludge pump 51.. Where larger amounts of reagents are intended to be introduced in this manner, it is desirable that they be introduced using steam or a second liquid immiscible with the reagent instead of air in the lines 53. It is an advantage of the embodiment illustrated in FIG. 5 that the zone of concentrated reagent activity extends downstream into the pump itself, the action whereof introduces a substantial amount of free energy to the pulp and dispersed reagent. Alternatively, as indicated in FIG. 6, the pulp may be forced through a venturi 6d, constituting the throat and expansion chamber 61 thereof as the zone of concentrated reagent activity. As a further alternative, nozzles 53 may be introduced directly to an ordinary line 76 carrying a suspension of material to be treated constituting the interior of the line for a space downstream of the point of introduction of the reagent as the zone of concentrated reagent activity.

In all of the immediately foregoing applications of the invention, additional energy input to the zone of concentrated reagent activity may be obtained by applying ultrasonic vibration, high frequency electrostatic or alternating electromagnetic fields to the exterior of the line adjacent the zone of concentrated reagent activity. The extent and nature of the additional energy thus supplied will depend upon the nature of the materials being treated and the purpose for which the treatment is being conducted. In general, the applications of the invention describe-d in conjunction with FIGS. 5, 6 and 7 are suitable for the treatment of a variety of oxide ores, hematites and calcites with fatty acid reagents or tall oils, or mixtures of fatty acid and tall oil. Where the material being treated consists of slimes from tailings dumps and the like where there is a considerable association of slime particles with larger particles to form rninor aggregations in the material of the pulp, ultrasonic vibration may be applied to the line immediately in advance of the introduction of reagent in order to disassociate the slimes from the larger particles to which they maybe adhering.

In FIGS. 8 and 9 are illustrated novel alternative forms of apparatus which are particularly adapted to carry out the method of the present invention.

Referring particularly to FIG. 8, the mixing chamber 8% is connected by means of a rubber flange 81 to a line 82 through which is being fed a pulp of the material to be treated preferably at a high solids liquid ratio (i.e. up to -75% solids). The mixing chamber is also connected to discharge line 83 through the rubber flange 84. A plurality of nozzles 65 supplied by lines 86 and 87 are directed into the interior of the mixing chamber t! 80 adjacent the inlet end thereof while the body of the mixing chamber 80 is surrounded with the generators 88 which consist of a plurality of ultrasonic vibration generators, or which may alternatively be generators of any other selected form of high energy oscillation. In operation, the incoming reagent dispersion from nozzles 25 is intimately mixed and dispersed in the pulp coming into chamber 8% from line 82. As this mixing action is taking place, the energy from the generator 88 will be assisting both the mixing action and by the release of energy within the pulp, the association of the reagent with the particles of mineral. A typical application for an apparatus of the type illustrated in FIG. 8 is that of the treatment of manganese or hermatite ore from a tailings darn with tall oil for subsequent flotation.

In FIG. 9, a special unit is illustrated adapted to be connected by rubber flanges 90 and 91 in a line carrying pulp of a material to be treated. The device illustrated has an inlet duct 92 leading to a venturi throat 93, which in turn leads into the expansion chamber 94. Ultrasonic generators 5 are situated around the inlet duct ,2 to disassociate slimes within the pulp from larger particles to which these slimes may be adhering. A plurality of nozzles 96 are directed into the throat of the venturi 93, these nozzles 96 being supplied by the two supply lines 97 and 98. The zone of concentrated reagent activity is formed within the expansion chamber 94 Where the high turbulence not only produces eflicient mixing of the reagent dispersion with the pulp, but also builds up high "electrostatic forces and mechanical forces due to the friction produced Within the pulp. The latter action may be augmented by means of pulse generators i fi placed around the expansion chamber generating as may be appropriate either ultrasonic, high frequency electrostatic or electromagnetic pulses. In many cases steam may be used as the vehicle for the reagent dispersion adding to the available energy in the zone of concentrated reagent activity both by elevating the temperature and in the production of shock waves as it condenses.

In addition to its use which has already been described in some detail for purposes of conditioning refractory materials for flotation operations, the method of the present invention lends itself to a variety of other applications. For instance, in the conditioning of magnetite for Wet magnetic separation, the reagent sodium silicate may be introduced through line 96 as a dispersion either in air or in water, and the application of sodium silicate to the particles of the pulp which takes place in the zone of concentrated reagent activity which is present in the expansion chamber 94 produces a complete dispersion of the magnetite allowing each particle of the pulp to move independently under the influence of the magnetic field in the subsequent magnetic separation step.

With suitable modifications to enable the handling of corrosive materials, an apparatus such as that illustrated in FIG. 9 may be used in the employment of the process of the present invention in order to carry out a leaching operation.

As is well known, conventional leaching involves the use of great volumes of liquid and long hold-up times. The reason for this is that in order to achieve adequate wetting of the material to be leached a relatively large volume of Water is considered necessary. In order to maintain reagent costs within economic limits, the concentration of reagent in the leaching baths is comparatively low. As a result, the solution time of the soluble constituents of the material being leached is correspondingly long. By utilizing the method of the present inven tion, it is possible to disperse a small volume of relatively concentrated reagent throughout a mass of relatively dense pulp so that the reagent is available throughout the mass at a relatively high concentration. It is further possible by the application of external energy such as ultrasonic vibration to overcome the air solid and air liquid interfaces which are the result of imperfect wetting with the effect that not only is the leaching time reduced to the point Where the solution of the materials to be leached can take place almost instantaneously, but this result is achieved with a minimum amount of dilution so that the total volume of solution resulting from the leach is very materially reduced and the values in such solutions are very materially more concentrated than is presently possible by conventional methods.

in FIG. 10, there is illustrated a typical leaching circuit employing the method of the present invention for the application of the leachant.

Referring more particularly to *FIG. 10, 1M indicates a slurring tank equipped with a suitably motivated high speed impeller 101. material is delivered by a controlled rate by the belt conveyor ltlZ. Also being delivered to the slurry tank Mill is liquid through pipe 163. The resulting slurry Which is at as high a solids liquid ratio as is possible is fed downwardly through the conduit 1% by the screw lltiS where it is introduced to the apparatus component 1% which is preferably similar in construction to the apparatus illustrated in FIG. 9. The leachant in highly concentrated form is produced as a dispersion either in the pure form in air or steam or in the form of droplets of concentrated solution of leachant in liquid substantially immiscible with the liquid of the pulp (i.e. which will be capable of maintaining itself as a separate phase in the pulp at least while the latter is passing through the zone of concentrated reagent activity). As the droplets of concentrated reagent disperse throughout the body of the pulp in the zone of concentrated reagent activity, the leachant will rapidly commence dissolving in the pulp liquid. Where the dissolution of the leachant is exothermic, the heat of solution for a finite period of time raises the temperature substantially in the region of each droplet of dispersed reagent. With the aid of the turbulence created in the mixing chamber and the externally introduced energy, the droplets of leachant will rapidly approach a state of uniform dispersion throughout the mass of pulp before the dilution of the leachant has proceeded to a very substantial extent, thus exposing each particle of mineral to be leached to a concentrated solution of leachant under conditions highly suited to an immediate attack of the mineral by the leachant, and cansing substantial completion of the solution of values before the pulp has finished passing through the mixing chamber. The pulp and leaching liquid discharged from the apparatus component 106 is passed through the line 107 to the filter 108 and the liquid discharged from the filter represents a concentrated pregnant solution, which is drawn off through line 169. The filter cake is resuspended in tank 110 which is the first tank of -a three stage countercurrent filtration washing circuit, the make-up water for which is introduced to the third tank 111 through line 112, which tank discharges a filter cake which is a final tailing. The liquid from the tank 110 is recycled to line 103 and becomes the make-up liquid for the original slurry in slurry tank liltl.

In FIGS. 11, 12 and 13, there is illustrated in diagrammatic perspective the application of reagent according to the process of the present invention to material in the course of its passage through a Wet comminution unit, i.e. a ball mill. Referring to FIG. 13, crushed mill feed is fed by conveyor 13th to the feed hopper 131 of ball mill 132. An air dispersion of reagent is directed into the feed hopper by spray or fog nozzles 133 in order to apply reagent in the dry condition to those slime sized particles of material as occur naturally in the feed. Within the wet ball mill 132 is suspended a reagent header 134 (note FIG. 11) having a number of downwardly directed nozzles 135 (note FIG. 11) adapted to spray a dispersion of reagent on to the downwardly moving portion of the charge within the mill whereby to establish along the length of the mill a zone of concentrated reagent activity To the slurry tank ltiil particulate 135:: (note FIG. 12) along the toe of the charge making use of the comminuting action of the mill, which is greatest at the toe of the charge to assist in the application of reagent to the particles of material as the latter are reduced to the point of mineral liberation. Where a lower than normal fall charge is used, and there is a free pulp zone in the mill, the nozzles may project below its surface of the free pulp zone. Additional reagent dispersion may be added by nozzles 136 which are submerged below the surface of the launder 137 and further additional nozzles 140 are directed downwardly and submerged below the surface of the outlet 138 of the classifier 139, which is associated with the milling circuit.

It will be appreciated from the foregoing that the present invention provides a novel, effective method for the application of reagent to particulate materials where the latter are in the form of a pulp. It will further be appreciated that the invention is one of broad application and that it is not to be construed as being limited merely to the specific applications which have been given herein by way of illustration.

What is claimed is:

1. A method for the flotation of finely divided minerals which comprises, forming a pulp of a finely divided mineral in a first liquid, providing a second liquid comprising a mineral flotation treating reagent effectively immiscible with said first liquid and feeding a mechanical dispersion of said liquid mineral flotation treating reagent in a finely divided state into a selected zone of said first liquid, applying ultrasonic vibration to the finely divided reagent is a sulphidizing agent.

4. The method as claimed in claim 1 wherein said liquid reagent is a dispersing reagent.

5. The method as claimed in claim 1 wherein the me chanical dispersion of the liquid flotation reagent comprises a solution of a water-soluble liquid in a liquid effectively immiscible with the first liquid.

References Cited by the Examiner UNITED STATES PATENTS 2,093,898 9/37 Toplin 209-166 2,362,670 11/44 Schulz 23-134 2,367,946 1/45 Kaercher 23-134 2,438,204 3/48 Castner 23-285 2,655,436 '10/53 Bishop et a1. 23-285 2,725,985 12/55 Howard et al. 209-166 X 2,743,289 4/56 De Boer et al 23-1 X 2,753,045 7/56 Hollingsworth 209-170 HARRY B. THORNTON, Primary Examiner. 

1. A METHOD FOR THE FLOTATION OF FINELY DIVIDED MINERALS WHICH COMPRISES, FORMING A PULP OF A FINELY DIVIDED MINERAL IN A FIRST LIQUID, PROVIDING A SECOND LIQUID COMPRISING A MINERAL FLOTATION TREATING REAGENT EFFECTIVELY IMMISCIBLE WITH SAID FIRST LIQUIDF AND FEEDING A MECHANICAL DISPERSION OF SAID LIQUID MINERAL FLOTATION TREATING REAGENT IN A FINELY DIVIDED STATE INTO A SELECTED ZONE OF SAID FIRST LIQUID, APPLYING ULTRASONIC VIBRATION TO THE FINELY DIVIDED REAGENT ENTERING SAID ZONE, MAINTAINING WITHIN SAID ZONE A LOCALIZED CONCENTRATION OF SAID MENERAL FLOTATION TREATING 